Directional plasma etching used for deep, high-aspect-ratio features. Alternating fluorine-based silicon etching and sidewall passivation is one implementation; transport, mask erosion, charging, scallops and aspect-ratio-dependent etch rate constrain the achievable structure.
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Deep reactive-ion etching (DRIE) is a semiconductor fabrication process used to create deep, well-defined structures in silicon and other materials. It is a variation of the reactive-ion etching (RIE) process, specifically designed for etching high aspect ratio features—where the depth of the etch is much greater than the width of the feature.